Manchester United Transfer News: Huge Thomas Muller Blow Amid Chelsea Rumours

Thomas Muller has been branded "irreplaceable" by the Bayern Munich hierarchy amid interest from Premier League giants Manchester United and Chelsea.

The German forward has long been targeted by United manager Louis van Gaal, and it recently emerged that Chelsea are looking at Muller as a replacement for the out-of-form Diego Costa, per Darren Lewis of the Mirror.

However, both clubs have been dealt a big blow with Bayern sporting director Matthias Sammer ruling out any possibility of Muller leaving the Allianz Arena, per the Evening Standard's James Benge:

"Thomas Muller embodies everything which distinguishes FC Bayern Munich. He is an absolute role model, an absolute gem and he's irreplaceable."

United need added firepower in attack and have been linked with a move for Southampton's Sadio Mane in January, per Bleacher Report's Dean Jones.

However, Muller would be a far more high-profile signing, and he is the type of superstar who could propel the Red Devils towards the top of European football once again.

Their current forward stars are either wildly out of form—see Wayne Rooney—or too inexperienced to be relied upon consistently.

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The likes of Anthony Martial, Memphis Depay and Jesse Lingard have shown flashes of brilliance this season but are far from world-class players at the moment.

Muller, on the other hand, is a genuine superstar. He has four Bundesliga titles, a Champions League and a World Cup and is still only 26.

This season he has netted 13 times in 14 German top-flight appearances, per WhoScored.com.

His creativity and goalscoring prowess have made him one of the most highly rated forwards in Europe, and United would likely be willing to splash out in excess of £50 million for him as he could be a major asset at Old Trafford for the next four or five years.

However, Muller also remains a vital cog in the Bayern machine, and they are clearly unwilling to even entertain the idea of letting him go.

He is contracted to the German giants until 2019, and no matter how hard they try it looks as though United will be unable to prise Muller away from Munich any time soon.